Telephotographic sending apparatus



Oct. 27, 1925. 1,558,672

R. HART TELEPHOTCGRAPHIC SENDING APPARATUS Filed July 2. 923

inventor; flusseZZ Hart,

A tzforney.

State of California,

and among its salient objects to accomplish the Patented Oct. 27, 1925.,

UNITED STATES PATENT OFFICE.

nussnu. 11am; or LOS mamas, oALn-onm Application filed July 2, 1923. Serial No. 848,088.

To all whom it may concern:

Be it known that I RUSSELL HART, a citizen of the United States, residing at Los Angeles, in the county of Los Angeles and have invented a new and useful Telephotographic Sending A paratus, of which the following is a speciE cation.

My invention relates to telephotography, are; first, to provide improved means for modulating energy waves in such a way as to adapt them for the reproduction of drawings, photographs, printed matter, and the like, at a 15 remote point by the methods of telephoto raphy; second, to afford facilities for sen ing out this modulated energy either by .radio, wired radio, or wired systems, as conditions may make most desirable; and, third, above results through the medium of relatively simple and thoroughly dependable apparatus. Other objects and "advpintages of my invention'yvill appear herema er.

as It is to be understood that, while I illustrate and describe herewith a preferred means for accomplishing my objects, I do not limit myself to the specific forms and arrangements disclosed. Various changes and adaptations may be made therein without departing from the spirit of my invention as hereinafter claimed.

My objects are attained by the apparatus illustrated in the accompanying drawing, which is to be considered as diagrammatic throughout, rather than strictly pictorial. In this drawing-.

Figure 1 is a side elevationaldiagram of the arrangement of the mechanical and optical parts of my apparatus;

Figure 2 is a WlllIlg diagram showing the circuits and connections of the electrical.

portions of the apparatus; v

Figure 3 is a diagram illustrating the manner in which a radio frequency energy wave is modulated by my improved means; Figure 4 is a diagrammatic view, of a fragment of photographic film indicating the mannerin which it is employed by me for photo-modulating energy;

Figure 5 is a side elevation of a preferred form of mounting for the photo-electric cell used as a necessary part of the equipment;

ferred form of photo-electric cell for connection with my apparatus.

' graphed or printed Figure 6 is a plan view of the above mounting, showing the manner in which it is made to traverse the photo-modulating field of operation; and

Figure 7 and Figure .8 respectively are front and side elevational views of a preuse in Similar reference numerals refer tosimilar arts throughout the several views.

T e present invention concerns itself only with tele-photographic sending apparatus.

It comprises; first, means for projecting.- strong images of the graphs to be transmit ted upon a plane, and for causing these images to repeatedly move across the plane at a uniform speed; second, means for causing a photo-electric cell to move uniformly across the plane perpendicularly to the direction of motion of the images; and, third means for causing the cell to modulate a suitable electric current, or a suitable series of electrical impulses, in a the light variations in the images.

The photo-electric cell in efi'ect is made to traverse the optical images in successive closely spaced parallel stri s, ultimately covering substantially the w ole areas of the images. By means of the variation of the light intensity falling upon the cell I thus producecontinuously photo-modulated electrical energy that may be transmitted and utilized for distant photographic reproduction of the ori 'nal images;

. In the-embofment of my invention selected for illustrative rent film 11 bearing the matter to be are focused by plane 13 of an maginary screen, so that graphical matter greatly enupon the film i projected as a larged image upon this plane,

The film may be the ordinary form of photographic film used in the motion picture industry,=or it may be a strip of tracing-linen or other transparent or translucent material suited for mitted.- The latter may be drawn, hoteupon the film. op

manner that corresponds to a otoglraphed. The light rays, after the matter to be trans-- purposes I em 'loy a powerfu'l source of illumination, suc as the arc lamp 9, and by means of condensing lenses 10 tical film is made up in the form of a relatively short endless belt of definitely determined length, and having uniformly spaced perforations 14 at each of its edges for controlling its motion.

The film runs upon four, gear-driven, sprockets having pin teeth at each end for meshing with perforations 14. Two of these sprockets viz, 15 and 16, revolve about axes perpendicular to the axis of lenses and on a posite sides thereof. The other two sproc ets, viz., 17 and 18 have their axes in a lane parallel to the lens axis, and on one si e thereof. The film in passing from one set of these sprockets to the other takes a quarter turn, and is at the same time turned inside out, so that one side of the film runs upon sprockets 15 and 16, and the other side upon sprockets 17 and 18. This arrangement allows using a short length of film belt and puts the return ortion of the belt outside the path of the lig t rays, which thllis pass through the film at the point 19 on y.

Each of the four sprockets is provided with a pair of small spring constrained rollers 20, for keeping the film upon their respective surfaces, and in mesh with their sprocket teeth. This permits of using the uarter turn inside-out twists 21, without danger of displacement or disengagement.

The film runs under slight tension through apressure gate 22, where it intersects the light rays. Its continuous, relatively rapid, motion prevents burning at this point, and the gate may be artificially cooled if desired. Uniform speed is imparted to the film by the synchronous motor 23, acting through the spur gears 24, and bevel trains 25 and 26. These are diag ammatically depictedin Fig. 1.

A simple and satisfactory form of photoel ctric cell is shown at 27, and most clearly in Figs. 7 and 8. This comprises a platinizcd strip 28 on a glass cover plate 29, the strip being etched down to the glass in such a manner as to. form a very fine interlaced grid 30, the two halves of which are not i contact. The interstices are then filled with selenium or other photo-active materia The strips are provided with terminal wires 31. and the photo active material is enclosed in a glass or porcelain cup 32 containing calcium chloride, cemented to. the back of the cover plate.

tion 35 adapted to rest upon, and be en-. gaged by the feed screw 36. By means of Other forms of photo-active cells such, for example, as

the latter, the modulating device may be i made to traverse the screen plane in a di rection perpendicular to the direction of motion of the film images.

Feed screw 36 is positively driven by motor 23, as by the worm and sprocket gearing indicated at 37. The carriage 33, when it has reached the end of its travel, may. be quickly returned toits starting position by lifting the half nut portion clear of the feed screw, and-sliding it back on the shaft 34. i

- Flexible shaft couplings are indicated at 3 8, and are usually found to be a convenience in installation and to reduce vibration. The various gearing ratios of the apparatus are so chosen that film 11 makes one" complete revolution, that is it completes one completecycle of its movement, concidently with one complete revolution of feed screw 36. Consequently. the photo-electric cell ismadeto traverse the recurring moving images in plane 13 along lines corresponding to the dotted lines 39 in Fig. 4. The. Width of grid 30 may be made equal, or

features of my invention, and the manner in which they may be connected, is illustrated in the diagram of Fig. 2. There are three complete and separate groups of cir-. cuits indicated, viz; an energy modulating group at theleft of inductive coupling 40; an amplifying group to the right. of this coupling; and a transmission circuit inductively coupled to the amplifying group, at 41 The energy modulating group as here shown, is made up of a re-generative oscil lating circuit containing the photo-modulltl lating means. This group comprises; a

three-electrode thermionic tube 42; inductance 43; transformer 44; two variable ca- 7 5 pacities 45 and 46; filament" battery 47 plate battery 48; photo electric cell 27; and primary coil 49 of inductive coupling 40.

The'tube filament 50 is connected directly across battery 47. The tube grid 51 is connected through inductance 43,. and coil 52 of transformer 44 in series, tofilament 50. The tube plate 53 is connected through'ba tery. 48, photo-cell 27, primary coil 49.0f inductive coupling 40, and coil 54 of trans former 44, in series, to filament 50. Ca-

pacity 45 shunts inductance 43 and coil 52.

- primary coil 49.

Oapabity 46 shunts the photocell 27 and pulses consists 1n varying their. am litude' in the manner indicated m Fig. 3, y the action of the photoelectric cell.

It is well known that selenium, in common with similar photoractive substances changes its resistance greatly when acted upon by light rays. As here used the selenium is in the form of a'sinuous filament of reat tenuity, bri ging grid 30. A very large proportion of its substance is thus subjected to the action of the light rays, and it is very quick to respond to variations in thelight intensity by changing itsresistance. The direct current impulses passing this varying resistance are modulated in am litude and we thus have, in efiect, impos an irregular light'modulated energy wave upon-a unidirectional radio-frequency wave 56.

The amplifying group 'of' circuits comprises; a three-electrode thermionic tube 57; secondary coil 58 of inductive coupling 40; primary coil 59 of inductive coupling 41; filament battery 60; grid battery 61; plate battery 62; lvariable capacity 63; grid. leak 64; and rheostat 65.

The tube filament 66 is connected across battery 60 with rheostat inseries. The tube grid 67 is connected throughgrid battery 61, capacity 63, and secondary inductive coupling coil 58, in series, to the filament 66; and grid leak 64 is connected as a' shimt between the grid and the filament. The tube plate 68 is connected to filament 66 through battery 62, and primary coil 59 of inductive coupling 41, in series.

This group of circuits amplifies the m0du lated energy wave received inductively through coupling 40, and delivers it, unchanged in form but increased in power, to

the transmission circuit, through the medi-v um of inductive coupling 41.

The transmission circuit receives its energy inductively through secondary coil 69 from the amphfyin group of circuits, in the manner just ex ained. This energy is in the form of a re atively powerful radiofrequency wave of modulated amplitude. It can therefore be transmitted to a distant receiving station either by radio, wired radio, or wired circuits, by methods well known in this art. coil 69, are suitably The terminals 70, of

energy to the ty ibimeeting the conditions en-' images in plane since, by reason of the relative connected to deliver the of transmission considered most desirable countered.

The foregoing description will enable anyone who is familiar with the arts of radiotransmission and telephotography, as hitherto developed, to clearly understand the arrangement of the constituent elements of my invention, and co-ordination of their operation, Further descri tion and elaboration of details is there ore considered superfluous; I desire however to call particular attention to the following'advantageous features'that mightotherwise be overlooked.

The great magnification of the graphical 13 permitsbfthe use of a photo-electric grid of practical dimensions which at the "same time is so small in proportion to the size of theimages that in relation thereto it corresponds to but a small and relatively great length,

point The rectangular shape of the grid permits-covering a very large percentage of the image areas, total area.

The'location of the photo-electric cell far in contact with the film closely approaching the films, and

the other evils'that the older method is 'subject to. The effects of slit refraction are also avoided.

7 An enormous amount of light may be concentrated upon the film in the y rapid mofilm, it is not ex osed to the high temperature long enoug to become dangerously heated. The heat accumulated during the brief time of its exposure is radiated throughout the remaining, relatively great, portion of its cycle of revolution.

Finally I desire to point out that it is perfectly feasible to water-cool orotherwise cool the pressure gate, and also the photoelectric cell, if this sh uld be found to be tion of the necessary.

I claim a my invention:

1. Apparatus of the character described comprising; means for projecting optical images upon a lane; an oscillating circuit including a f oto-electric cell and an audion, where y a photo-modulated current may be produced; and means for causing said cell to traverse said plane for modulatin said current; said cellv being connecte in the plate circuit of said audion.

2. Apparatus of the character described ressure gate comprising; means for projecting optical images upon a plane and causing them to traverse 1t; an oscillating clrcuit including a photo-electric cell and an audion, whereby a photo-modulated current may be produced; and means for causing said cell to l traverse said plane transversely to the di rection of motion of said images for modulating said current thereby; said cell being connected in the plate circuit of said audion.

-"3. Apparatus of the character described comprisin a movable optical film with graphs thereon; means for projecting images of said graphs upon-a plane; an oscillating circuit includin a photo-electric, cell and an audion, whereby a photo-modulated current may bc'produced; and means for causing said cell to traverse said plane 'transversely to the direction of motion of said film, 'for modulating said current; said cell being connected in the plate circuit of said audion. p

1. Apparatus of the character described comprising; an endless rotatable optical film 25 with graphs thereon; means for projecting.

images of said graphs upon said plane;

means for uniformly rotating said 111m to cause-said images to traverse said plane; an oscillating circuit including a photo-electric cell and an audion, whereby a photo-modulated current may be produced; and means for causing said cell to traverse said plane at a uniform speed transversely to the direction of motion of said images, for modulating said current; said cell being connected in the plate circuit of said audion.

5. Apparatus of the character described comprising; means for projecting recurring optical images upon a plane and causing them to traverse it at a uniform speed in registering paths; an oscillating circuit including a photo-electric cell and an audion, whereby a photo-modulated current may be produced; and means for causing said cell to traverse said plane at a uniform speed transversely to the direction of motion of said images 'for modulating said current; said cell being connected in the plate circuit of said audion.

RUSSELL HART. 

